1. Field of the Invention
The present invention relates generally to health monitoring systems, and in particular to health monitoring systems for personnel on a boat, where the boat is capable of operating at high speeds and can be deployed in warfare special operations.
2. Prior Art
Advancements in high speed craft (HSC) construction and powering technology have led to ever-increasing craft speed and increasing numbers of reported impact injuries. The military HSC impact injury problem is particularly insidious since, unlike their civilian high speed pleasure craft and offshore racing counterparts, military crewmen must operate their craft at high speed in rough seas to fulfill their mission and, at times, to survive. Further, as military craft, the crewmen generally agree that they must “train as they fight.” A critical objective within a human-centered approach to HSC acquisition is to reduce the incidence of impact injury.
Ron Peterson et al. in an article entitled “Evaluation of Criteria for Assessing Risk of Impact Injury in High Speed Craft” published Feb. 3, 2006, reports that Gollwitzer and Peterson [Gollwitzer, R. M., and Peterson, R. S., (1994) Shock Mitigation on Naval Special Warfare High Speed Planing Boats Technology Assessment, Report CSS/TR-94/33, Dahlgren Division, Naval Surface Warfare Center, Panama City, Fla.] described the effects of repeated shock impacts on occupants during high speed operations in Naval Special Warfare boats. Ensign et al. [Ensign, W., Hodgdon, J., Prusaczyk, K., Ahlers, S., Shapiro, D., and Lipton, M., (2000) A Survey of Self-Reported Injuries Among Special Boat Operators, Report TR 00-48, Naval Health Research Center] found compelling evidence of a significant injury problem in a study of self-reported injuries of high speed boat operators. It was found that 65% of operators responding to the survey sustained boat-related injury, with 89% of these within the first two years of operation. This injury problem is both acute and chronic, reducing both the short-term and the long-term effectiveness of personnel who are exposed to repeated shock impacts.
Sea trials performed in January 2003, October 2003, and January 2005 provide data upon which the relative performance of discomfort methods (RMS, ISO 2631 Part 1 (1985), and ISO 2631 Part 1 (1997) VDV) and injury assessment methods (ISO 2631 P5) may be evaluated. In these sea trials, boat deck, seats, human volunteers and Hybrid III anthropomorphic test dummies were instrumented with tri-axial accelerometers and tri-axial angular rate sensors. The Hybrid III dummies also contained lumbar and cervical spine load cells. The RMS, ISO 2631 Part 1, and ISO 2631 Part 5 were all evaluated at the seat pad of the occupant. However, discomfort and injury relevant to this work is related to accelerations and the corresponding forces of the lumbar spine. Often discomfort is a sign of the initiation of an injury; however this is not always the case. In this study it was found that the RMS of the seat pad accelerations does not account for human spine dynamics, nor does it accurately account for severe discrete events that are common with high speed planing boats, like a Mark V Special Operations Craft (MK V SOC) and Naval Special Warfare Rigid Inflatable Boat (NSW RIB). These high speed craft are capable of speeds of 45 knots and higher. Also, while MK V SOC can have suspended seats, NSW RIBs do not, and the personnel substantially spend most of their time standing.
The ISO 2631 Part 5 is the only existing criterion to include transfer functions for predicting tri-axial lumbar spine accelerations from measured seat pad accelerations. Within the ISO 2631 Part 5 standard, lumbar forces are estimated from the predicted lumbar accelerations. These forces are correlated to a likelihood of injury based upon the ultimate strength of the lumbar spine, the variance of this strength, and probability analysis. Lumbar spine accelerations (which are often approximated by exterior back accelerations corresponding to the L4 lumbar spine) and the measured lumbar spinal forces in the Hybrid III dummies can be compared to predicted values from the ISO 2631 Part 5 as a way to validate the standard.
The ISO 2631 Part 5 is stated as the best injury criterion available to assess impact spine injury on high speed craft. However, injury reference values in the ISO 2631 Part 5 may be too low, especially for military operators. An analysis of predicted and measured lumbar forces, coupled with anecdotal information concerning ride quality from experienced crewmen will help lead to the identification of appropriate injury thresholds for occupants of high speed craft.